This invention relates to a high current power supply apparatus primarily used to power a motor to drive a vehicle such as a hybrid or electric car.
A high current, high output power supply apparatus used as a power source for a motor to drive an automobile contains power modules. Power modules are a plurality of series connected batteries, and they are in turn connected in series to raise the output voltage of the power supply apparatus. The purpose of this is to increase the output of the driving motor. Extremely high currents flow in a power supply apparatus used for this type of application. For example, in a vehicle such as a hybrid car, when starting to move or accelerating, battery output must accelerate the car, and extremely high currents over 100A can flow. High currents also flow during short period, rapid charging.
In a high current power supply apparatus, forced cooling is required when battery temperature rises. In particular, in a power supply apparatus with many power modules inserted in vertical and horizontal columns and rows in a holder-case, it is important to uniformly cool each power module. This is because performance degradation will result for a battery which rises in temperature when battery cooling is non-uniform.
Systems which house a plurality of power modules in a holder-case and cool each power module more uniformly are cited, for example, in Japanese Patent Applications HEI 10-270095 (1998) and HEI 11-329518 (1999). As shown in the cross-section view of FIG. 1, the power supply apparatus of the former application cools internally housed power modules 121 by forcing air to flow from air intakes 123 which form the base of the holder-case 122 to exhaust outlets 124 which form the top of the holder-case 122. Cooling adjustment fins 125 are disposed inside the holder-case 122 to adjust the speed of air flowing over the surfaces of power modules 121.
In a holder-case 122 of this configuration, air flows more rapidly over the surfaces of power modules 121 disposed near the top than those near the bottom. The purpose of this is to avoid a temperature differential between power modules 121 at the top and bottom. If the flow rate of air passing over the surfaces of power modules 121 at the top and bottom is made the same, power modules 121 at the bottom will be cooled more efficiently than those at the top because air flowing over the surfaces of power modules 121 at the bottom has a lower temperature.
To make the flow rate of air over power modules 121 at the top faster than the flow rate over those at the bottom, the gap for air flow between the cooling adjustment fins 125 and the power modules 121 is gradually made narrower towards the top of the holder-case 122. This is because air flow becomes faster as the gap for air flow becomes narrower.
This type of power supply apparatus cools power modules near the bottom with cool air and power modules near the top with high flow rate air to establish a more uniformly cooled environment for power modules at both the top and bottom. However, it is extremely difficult to cool upper and lower power modules under very uniform conditions in this type of system. This is because the temperature of cooling air for power modules at the bottom is low, and the temperature of cooling air for power modules at the top becomes high. It is difficult to cool upper power modules with the same efficiency as lower power modules even by increasing the flow rate over power module surfaces when upper power module cooling air temperature has become high. For this reason power modules near the air intakes can be cooled efficiently, but power modules near the exhaust outlets are difficult to cool efficiently and this system has the drawback that temperature differential develops over power modules housed in the holder-case. This has the deleterious effect that power modules, which are near exhaust outlets and very difficult to efficiently cool, become hot and easily degraded.
As shown in the cross-section view of FIG. 2, the power supply apparatus cited in the later patent application directs cooling air into the holder-case 222 from intermediate positions along the holder-case 222. Air directed into the holder-case 222 from intermediate positions supplies cool air to regions near the outlet and makes the inside temperature of the holder-case 222 uniform. This system can reduce the temperature differential across the holder-case 222, but the flow rate of air inside drops due to air entering from intermediate positions along the holder-case 222. To efficiently cool power modules 221, it is important to lower the temperature of the cooling air, but it is also important to increase the flow rate of air over the surfaces of the power modules 221. Even if cooling air temperature is lowered, the region of air immediately in contact with the surface of a power module will rise in temperature if flow rate slows. Since a power module 221 is cooled by the air in immediate contact with its surface, it cannot be efficiently cooled if the temperature of this region of air becomes high.
The present invention was developed to correct these types of drawbacks seen in prior art power supply apparatus. Thus it is a primary object of the present invention to provide a power supply apparatus which can cool all of the plurality of power modules housed in a holder-case more uniformly and effectively prevent battery performance degradation caused by temperature differentials.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.
The power supply apparatus of the present invention is provided with a plurality of power modules, a holder-case which houses the power modules arranged in rows in a parallel fashion and which cools the power modules by passing air through the inside of the case, and a fan which forcibly supplies air to the holder-case or intakes air through the holder-case. The holder-case is box -shaped and has a first surface plate and a second surface plate disposed on opposite sides. A plurality of power modules are arranged side-by-side in line with the plane of the first and second surface plates in a plurality of columns. Further, walls are established between the plurality of power modules laterally arrayed in the holder-case. The walls are located between the first surface plate and the second surface plate. The interior of the holder-case is divided into a plurality of columns of partitions by the walls, and power modules are disposed in each partition column. The surfaces of partition walls facing power modules follow the contour of the surfaces of the power modules, and cooling ducts of uniform width are established between power module surfaces and partition walls facing the power modules. Air forced into the partitions has its flow directed along power module surfaces by the cooling ducts. In addition, the holder-case has flow inlets opened through the first surface plate to divide air flow and direct it into the cooling ducts of the plurality of partition columns. Exhaust outlets are also opened through the second surface plate to expel air which has passed through the plurality of cooling ducts. The power supply apparatus uses the fan to divide and divert air flow through the first surface plate flow inlets into the plurality of partitions, passes air through the cooling ducts to cool the power modules, expels air which has performed its cooling function through second surface plate exhaust outlets, and thereby cools the power modules disposed inside the plurality of partition columns.
This configuration of power supply apparatus has the characteristic that all of the plurality of power modules housed in the holder-case can be more uniformly cooled, and battery performance degradation caused by temperature differentials can be effectively prevented. This is because the power supply apparatus of the present invention divides the interior of the holder-case with walls into a plurality of columns of partitions, disposes power modules in each partition column, establishes cooling ducts of uniform width via partition walls which follow power module contours, and causes air forced into the partitions to flow along power module surfaces via the cooling ducts. Since the cooling ducts in this configuration of power supply apparatus are uniform in width, the flow rate of air in the holder-case does not decrease and power modules can be efficiently cooled. Further, since the cooling ducts of this power supply apparatus are made to follow the surfaces of the power modules, air flowing through the cooling ducts has to make direct contact with all regions of the surfaces of the power modules, and cooling can be extremely efficient and uniform.
In a power supply apparatus of the present invention, cooling ducts can be made uniform in width around the entire perimeter of each power module. Further, it is preferable to arrange the plurality of power modules in a parallel fashion and in an array with a plurality of rows and a plurality of columns inside the holder-case of a power supply apparatus of the present invention.
The plurality of power modules of a power supply apparatus of the present invention may be housed in the holder-case in a two row array, In that case, at least one dead air space can be established in the upstream partition of the first row disposed on the side of the first surface plate. In this power supply apparatus, the downstream partition cooling ducts can be made nearly constant in width over approximately the entire power module circumference, and the width of the upstream partition cooling ducts can be made wider than the width of the downstream partition cooling ducts to establish at least one dead air space. The upstream partition cooling ducts can be made nearly constant in width over approximately half the power module circumference, in the remaining half they can be made wider to establish dead air spaces. The dead air spaces can be established on the downstream side of the upstream partition. Further, a plurality of dead air spaces can be established around approximately the entire power module circumference in the upstream partition. The upstream partition can be square-shaped in a cross-section view to establish a dead air space at each part of its four corners. Furthermore, the width of cooling ducts between the upstream and downstream sides in the upstream partition can be equal to the width of cooling ducts of the downstream partition.
Further, in a power supply apparatus of the present invention with a plurality of power modules housed in the holder-case in a two row array, a bypass may also be established to direct air flow from the upstream partition of the first row adjacent to the first surface plate to the downstream partition of the second row adjacent to the second surface plate.
Still further, in a power supply apparatus of the present invention with a plurality of power modules housed in a plurality of rows in the holder-case, the plurality of power modules in adjacent rows may also be offset.
It is preferable to provide retaining projections extending from partition walls facing power modules. The ends of these retaining projections contact the surface of a power module and hold that power module in place inside the partition.
Finally, it is preferable for the power modules and partitions to be shaped as circular columns, and disposition of power modules at partition centers can establish cooling ducts of uniform width.